# [R] sweave question

Daniel Nordlund djnordlund at frontier.com
Thu Feb 14 01:49:33 CET 2013

Mark,

just to be clear, since R uses the backslash character as an escape character inside strings, then any backslash that you want to appear in your latex code must be escaped, i.e. it must be doubled.  But any backslash character that is being used as an escape character should remain as a single character.

I looked at the solution you linked to, and it looks to me like the post got a little garbled in transmission.  Here is what I saw.

<<label=fig1, fig=FALSE, result = tex>>=
pdf("fig1.pdf", width = wid, heigth = hei)
plot(1:10)
dev.off()
cat("\begin{figure}\")
cat("\includegraphics[width = ", wid, ", height = ", hei, "]{proj1-fig1}\"}
cat("\end{figure}")
@

In the first cat(), the "\begin{figure}\" is not going to be interpreted properly.  the \b will be interpreted as an escape character, and so what will be printed is something like this (where '_' represents the escape sequence \b that I didn't look up)

_egin{figure}

In addition, you want to be writing the latex commands on separate lines, which requires that the string be ended with '\n', i.e. a newline character. But it looks like the 'n' got stripped out.  Also, the second cat statement in the example above ends with a '}' instead of a ')'. So I suspect that the example should have looked like this

<<label=fig1, fig=FALSE, result = tex>>=
pdf("fig1.pdf", width = wid, heigth = hei)
plot(1:10)
dev.off()
cat("\\begin{figure}\n")
cat("\\includegraphics[width = ", wid, ", height = ", hei, "]{proj1-fig1}\n")
cat("\\end{figure}\n")
@

If I have got any of this wrong, I am sure someone will come along and correct me.

Dan

Daniel Nordlund
Bothell, WA USA

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> On Behalf Of Mark Leeds
> Sent: Wednesday, February 13, 2013 4:18 PM
> To: Nordlund, Dan (DSHS/RDA)
> Cc: r-help at r-project.org
> Subject: Re: [R] sweave question
>
> thanks dan. I'll try the double slash on both sides when I get back later
> tonight. In the solution on
> the net, he only had the backslash on the end quotes ( well there was a
> backslash at the beginning but that's a real backslash  needed for latex
> commands ). I'll let you know how it works out. thanks again.
>
>
>
>
>
>
> On Wed, Feb 13, 2013 at 6:50 PM, Nordlund, Dan (DSHS/RDA) <
> NordlDJ at dshs.wa.gov> wrote:
>
> > > -----Original Message-----
> > > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> > > project.org] On Behalf Of Mark Leeds
> > > Sent: Wednesday, February 13, 2013 2:59 PM
> > > To: r-help at r-project.org
> > > Subject: [R] sweave question
> > >
> > > Hi Everyone: I was having trouble getting the plot size correct when
> > > putting a plot in an sweave document. So, I searched on the internet
> > > and I
> > > found a clever solution where the person uses
> > > the cat function to write latex code so he can include the cat code in
> > > the
> > > chunk and place the plot using width and height. The solution is here:
> > > https://stat.ethz.ch/pipermail/r-help/2009-April/195094.html.
> > >
> > > But the solution uses a backslash before the ending quotes in the cat
> > > statements  that might be windows relevant possibly ? I'm not sure
> > > that part but I'm on linux and when I tried my way to mimic that
> > > solution
> > > in the latex/sweave code below ( I think it's the same solution but
> > > without
> > > the backslash on the closing quotes. I tried that also but got a
> > > different
> > > error ) , Sweave doesn't like the start of the includegraphics
> command.
> > > The
> > > error I get from Sweave is
> > >
> > > #=======================================================
> > > Error:  chunk 9 (label = fig3)
> > > Error : '\i' is an unrecognized escape in character string starting
> > > "\i"
> > > Execution halted
> > > :~/research/equity/projects/tree_returns/report>
> > > #=====================================================
> > >
> > > The code is below but if anyone is interested and thinks they need the
> > > whole file to look at the problem, I can send it. I just didn't want
> to
> > > send the whole file here. Definitely the error has to do with the
> chunk
> > > below for sure ( even though it says chunk 9 because there is no chunk
> > > 9
> > > ).  Thanks a lot to anyone who can be bothered investigating because
> > > I've
> > > spent pretty much the whole day on this and think it's
> > > time to surrender !!!!!!!!!! or atleast give up for now and come back
> > > to it
> > > with a fresher brain. Have a good night.
> > >
> > > # THE LATEX/SWEAVE CODE
> > > #================================================================
> > >
> > > cal.tree is created in a previous chunk and that's fine.
> > >
> > > <<chunk08,label=fig3, fig=FALSE,result = tex>>=
> > > wid <- 5
> > > hei <- 5
> > > pdf("reg_tree-fig3.pdf", width = wid, height = hei)
> > > plot(cal.tree,uniform=TRUE,compress=TRUE,margin=0.0)
> > > text(cal.tree, all=TRUE,fheight=1.0,fwidth=1.0)
> > > dev.off()
> > > cat("\begin{figure}[ht!]")
> > > cat("\begin{center}")
> > > cat("\includegraphics[width = ", wid, ", height = ", hei,
> > > "]{reg_tree-fig3}")
> > > cat("\end{center}")
> > > cat("\caption{The resulting unpruned regression tree of the california
> > > real
> > > estate data}")
> > > cat("\label{FIG:figthree}")
> > > cat("\end{figure}")
> > > @
> > >
> >
> > Mark,
> >
> > I am not an sweave expert, but I think the problem is actually that you
> > need to double all of your backslash characters that you actually want
> to
> > write out as a backslash.  The error message says that it doesn't
> recognize
> > the escape character '\i'.
> >
> > Hope this is helpful,
> >
> > Dan
> >
> > Daniel J. Nordlund
> > Washington State Department of Social and Health Services
> > Planning, Performance, and Accountability
> > Research and Data Analysis Division
> > Olympia, WA 98504-5204
> >
> >
> > ______________________________________________
> > R-help at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
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